We request support to perform secondary data analyses on family data obtained in an ongoing hypertension genetic study conducted at the University of Utah (PI, Roger R. Williams MD). The available data represent on& of the largest study of cardiovascular reactivity among genetically related individuals. During 1981-83, a total of 2,548 subjects, members of 98 extended families (multiple generations and multiple nuclear families) participated in an extensive cardiovascular examination and were assessed on a comprehensive battery of cardiovascular tests. Annual follow-up questionnaires obtained information about the onset of hypertension and new medication prescribed. In 1991-92, a follow-up exam is being conducted on 1,500 subjects. Given recent advances in the analyses of genetic epidemiologic data, this available resource presents a unique opportunity to address timely issues pertinent to the contribution of genetic and environmental factors to individual differences in cardiovascular reactivity. Specific objectives of this proposal are: (1) to confirm or refute current hypotheses postulating a reactivity-hypertension association;(2) to investigate whether there is a sex limitation in the genetic and environmental determinants of reactivity;(3) to explore genotype-by-age interactions in the control of reactivity;and (4) to determine whether there is shared genetic and/or environmental variance between reactivity and other recognized cardiovascular risk factors (e.g., obesity, lipids). The proposed study has both methodological and clinical significance and can be done at minimal cost using the available data. We expect at least four publications to result from these analyses.